Glueless interlock carton construction and blank therefor



J. F. DION Dec. 18, 1962 GLUELESS INTERLOCK CARTON CONSTRUCTION AND BLANK THEREFOR Filed March 3, 1960 INVENTOR.

UOHN E DION BY 4 7M ATTORNY5 United States Patent f The present invention relates to carton constructions and more particularly to an improved interlock for holding adjacent side walls in assembled relation without the use of glue or other securing means.

7 The object of the invention is to provide a glueless corner construction for cartons which may readily be assembled by automatic means and which PIOVIdES a positive locking action regardless of possible inaccuracies in forming the blank from which the carton is made.

Another object of the invention is to provide a blank from which such corner construction-s can be formed.

The inventive features of the invention are characterized by an internal cut on one wall panel of a carton and a tongue for-med on a flap connected to an adjacent wall panel. The tongue is inserted into the internal cut with a camming action that forces the adjacent wall panel into firm engagement with the adjacent end edge of the one wall panel} A locking projection preferably extends from the upper end of the tongue and is snapped intenorly of the carton as the camming action is exerted.

The above and other related objects and features of the invention will be apparent from a reading of the following description of the disclosure found-in the accompanying drawing and the novelty thereof pointed out in the appendedclaims.

In the drawing:

FIG. 1 is a plan view of a blank embodying alternate forms of the invention;

FIG. 2 is an elevation of one form of the corner construction partially assembled;

FIG. 3 shows the corner construction of FIG. 2 assembled and ready for use;

FIG. 4 is an elevation of the other form of the invention seen in FIG. 1 showing the corner construction partially assembled; and

FIG. 5 shows the corner construction of FIG. 4 assembled and ready for use. a

In the following, the terms side, bottom and end will be used as terms of reference in describing certain walls or panels in the cartons embodying the present invention. Such terms are, of course, not limiting but merely for convenience in giving an understanding of the concepts involved herein. Referring now to FIG. 1, the carton blank is formed of cardboard or other relatively thick (as opposed to paper) sheet material that is employed to form cartons. The blank 10 is shown with one form of interlock for the left hand corners and another form of interlock for the right hand corners. Although this is a workable arrangement, it is contemplated that in a given blankit would be the usual practice to employ only one form of the invention.

The blank 10 comprises the usual panels required for forming open top boxes or trays. Thus there are a bottom panel 12, end panels 14, 16 and side panels 18, 20. The end panels are swingably connected to the bottom panel along hinge or score lines 26, 27, while the side panels 18, 20 are swingably connected to the bottom panel 10 along score lines 28, 29.

Next to be described are the means for locking the end panel 14 in assembled relation with the side panels 18, 20. Locking flaps 30, 32 are swingably connected to opposite ends of the end panel 14 along hingeline34, 36.

3,069,061 Patented Dec. 18, 1962 The flaps 30, 32 respectively comprise locking tongues 38, 40, the locking tongues respectively comprise camming edges 42, 44 and locking projections 46, 48. The side panels 18, 20 have at their ends adjacent the locking flaps 30, 32 end edges 50, 52. At this point it will be noted that the illustrated corner construction is a square corner and that the hinge lines 26 and 28 are at right angles to each other and that the edge 50 is at right angles to the hinge line 28 while the hinge line 34 is at right angles to the hinge line 26. It will also be noted that the hinge line 34 is offset from the hinge line 28 a distance roughly corresponding to the thickness of the blank. This offset relationship is standard practice and enables the lock flap 30 to be folded flush against the outer surface of the side panel 18. The same angular relationships also exist in the corner construction at the lower left hand corner of the flap.

Referring back to the side panel 18 it will be seen that an internal cut of bent outline defines a tongue 53. Actually the edges of this cut opposite the tongue 53 of the panel are the functional edges which are involved in the interlock of the corner construction. These edges comprise a vertical portion 54. An angled portion 56 which extends genenally upwardly and away from the end edge 50 and then a terminal portion 58 which extends generally downwardly and away from the end edge 50. In the panel 20 a similar internal cut forms a tongue 59 and edges 60, 62, 64 which respectively correspond to the edges or edge port-ions 54, 56 and 58.

Referring now to FIG. 2 the manner of assembling this corner construction may be better understood by a description of the interlock between panels 14 and 20. The side panel 20 is folded upwardly along the score line 29, end panel 14 is also folded upwardly along the score line 26 and flap 32 is folded inwardly along score line 36. As the panel 14 is folded upwardly the internal tongue 59 is deflected outwardly to permit the flap 32 to lie against the panel 20 with the tongue 59 overlying the tongue 40. For descriptive purposes FIG. 2 illustrates what could happen by a slight inaccuracy in the cutting die used in forming the blank 10. Thus it is shown that the edge 50 in this partially assembled position does not quite engage the panel 14. The lead lines for reference characters 60,. 62 and 64 are dotted in FIGS. 2 and 3 since the edges denoted underlie the tongue 40 and are coincident with the tongue 59. It will be noted that the caming edge 44 at its upper end is coincident with the angled cut edge 62 but that the edges 42 and 56 are not coincident but purposefully set at different angles so as to obtain a cam ming action. It has been found that an angular difference in the order of 4 between the edges 44 and 62 gives the most effective camming action. It has also been found thatan internal angle of approximately 45 between the edge 62 and the bottom panel 12 is to be preferred but is not as critical as the 4 relationship.

It will also be noticed in FIG. 2 that the projection 48 extends somewhat beyond the cut edge 64. With this preliminary assembly having been made it is a simple matter to complete the assembly of the corner construction by applying pressure to the internal tongue 59 adjacent its upper end. As this pressure is applied the projection 48 snaps past the cut edge 64 and as the camming edge 44 is pushed further in it progresses along the cut edge portion '62 tightly drawing the panel 14 into firm engagement with the edge 52 at the end of the panel 20 as seen in FIG. 3. The camming action positively holds the panel 14 against any movement relative to the panel 20 in the plane of said panel 20, while the locking projection 48 prevents the corner construction from coming apart completely should the edges 44 and 62 lose their grip on each other. The finished corner construction thus described is seen in FIG. 3.

The upper left hand corner is assembled in essentially the same fashion inasmuch as there is correspondency with the various elements at the lower left hand corner.

Referring now to the means for locking the opposite end panel 16 in assembled relation with the side panels 18 and 20 it will be seen that lock flaps 70, 72 are swingably connected to the end panel 14 along hinge lines '74, 76 and that locking tongues 78, 89 are formed on the flaps 7 0, 72. Curved cuts 82, 84 define the upper or camming edges of the tongues 78, 80 and locking projections 86, 88 extend from the tongues 78, 80. Cut edges 9%), 92 are formed on the ends of the panels 18, 20 adjacent the end panels 16 the right angle relationships of the hinge lines 28, 29, 74 and 76 relative to the hinge line 27 and the angular relationship of the end edges 96, 92 are the same as at the left hand end of the blank inasmuch as right angle corners are again to be formed at this end of the blank.

Internal cuts 94, 96 of bent outline define tongues 98, 99 in the side panels 18 and 20. The cuts 94, 96 are equivalent to the internal cuts at the opposite ends of the panels 18 and 20 in that they represent a blending of the three distinct portions previously described. Thus the cuts 94, 96 comprise a portion extending outwardly from the outer panel and away from the end edges 90, 92 and then a portion again extending away from the end edges 90, 92 and inwardly toward the bottom panel. In assembling this alternate corner construction the internal tongue 99 is deflected outwardly to receive the locking tongue 80 as the flap 72 is laid against the face of the side panel it) as the panel 16 is swung about score line 27 to an upright position. As can be seen from FIG. 4 the locking projection 88 overlies the face of the panel 20 and the upper edge of the camming edge 84 is coincident with the internal cut 96. tongue 80 overlies the greater portion of the internal cut 96 which is indicated by a dotted lead line for that reason. Thus when pressure is applied to the internal tongue 99 the projection 88 will be snapped interiorly of the panel 20 and the camming edge 84 will act against the internal cut 96 to force the edge 92 of panel 20 into firm engagement with the panel 16 as seen in FIG. 5.

In both of the described embodiments of the invention a simple manner has been provided for locking adjacent panels of a corner construction so that there will be no relative movement therebetween. This is of greater importance in obtaining a stronger box construction and is of particular advantage where the boxes or trays as herein described are to be overwrapped by an outer layer of wrapper material. herein described greatly facilitate-s neat and attractive overwrapping with automatic machines.

Having thus described the invention what is claimed as novel and desired to be secured by Letters Patent of the United States is:

1. A carton of the type wherein adjacent walls or panels are held together in assembled relation by a glueless interlock, said carton comprising:

(a) a main panel,

(b) a first wall panel folded upright from said main panel about a first hinge line, and

(c) a second wall panel folded upright from said main panel about a second hinge line which intersects said first hinge line,

(d) said first panel having an end edge normal to said hinge lines at the intersection thereof,

(e) said first panel having an internal tongue formed by an internal cut which also defines a cut edge in said first panel,

(1) said out edge having a first portion extending outwardly of said main panel,

(g) said out edge having a second portion connecting with the outer end of said first portion and lying on a straight line which intersects said first hinge line at :an acute angle facing toward the remote end of said It will further be noted that the locking The locked corner construction first panel, said straight line also being disposed relative to said first portion at an obtuse angle of less than facing toward the remote end of said first panel,

(It) said cut edge having a third portion connecting with the outer end of said second portion and ex-. tending back towards said main panel,

(i) said second panel having a locking flap folded against the outer face of said first panel about a third hinge line intersecting the intersection of said first two hinge lines,

(j) said locking flap having a locking tongue underlying said internal tongue and inserted through said internal cut into the interior of said carton,

(k) said locking tongue having an upper camming edge engaging the second portion of said cut edge in said first panel and maintaining said end edge of said first panel in engagement with the inner face of said second panel,

(I) the outer tip of said locking tongue extending a short distance beyond the outer extent of the second portion of said out edge,

(m) the camming edge of said locking tongue lying on a straight line which intersects said first hinge line at an acute angle facing toward the remote end of said first panel,

(11) the defined acute angle of said camming edge being approximately 4 less than the defined acute angle of the second portion of said out edge.

2. A carton of the type wherein adjacent walls or panels are held together in assembled relation by a glueless interlock, said carton comprising:

(a) a main panel,

(12) a first wall panel folded upright from said main panel about a first hinge line, and

(c) a second wall panel folded upright from said main panel about a second hinge line which intersects said first hinge line,

(d) said first panel having an end edge normal to said hinge lines at the intersection thereof,

(e) said first panel having an internal tongue formed by an internal out which also defines a cut edge in said first panel,

(f) said out edge having a first portion extending outwardly of said main panel,

(g) said cut edge having a second, concavely curved portion connecting at its inner end with the outer end of said first portion, said second portion being curved, toward its outer end, outwardly of said main Panel and away from the adjacent end of said first panel,

(it) said out edge having a third portion connecting with the outer end of said second portion and extending back towards said main panel,

(i) said second panel having a locking flap folded against the outer face of said first panel about a third hinge line intersecting the intersection of said first two hinge lines,

(j) said locking flap having a locking tongue underlying said internal tongue and inserted through said internal cut into the interior of said carton,

(k) said locking tongue having an upper convexly curved camming edge engaging the second portion of said cut edge in said first panel and maintaining said end edge of said first panel in engagement with the inner face of said second panel,

(I) the outer tip of said locking tongue extending a short distance beyond the outer extent of the second portion of said out edge,

(m) the curvature of the camming edge of said locking tongue generally matching the curvature of said concavely curved second portion of said cut edge,

(n) the tangents to said convexly curved camming edge and said concavely curved portion of said cut edge, at the point of engagement between said edges, form- 8,069,061 5 6 ing acute angles relative to said first hinge line, fiacing References Cited in the file of this patent toward the remote end of said first panel, (0) the defined acute angle of the tangent for said UNITED STATES PATENTS convexly curved camming edge being less than the 2,634,899 M611er Apt 14, 1953 defined acute angle of the tangent for the coneavely 5 2,712,409 Buttery July 5, 1955 purved Portion of said cut edge 2,889,102 Wagaman June 2, 1959 

